A number of cruise control systems for vehicles have been proposed or utilized in the past, but most of these have required relatively complex control systems which cannot be incorporated into existing vehicles without significant modification of the latter. Moreover, many such systems are useful either only with compression ignition engines or only with spark ignition engines, and have certain disadvantages in operation. It has been recognized that it is desirable that the driver of a vehicle be able to override a cruise control system for example when he wishes to overtake another vehicle or accelerate temporarily for some other reason. Although provision for this has been made in some known systems, exercise of such an override normally disengages the system which must be reset before it will resume control of the vehicle. Additionally, it is desirable that the cruise control system be automatically disengaged should the driver apply the brakes of the vehicle. It would also be desirable to ensure that the system is disengaged when the vehicle is descending a steep hill, or should the vehicle be suddenly decelerated for any other reason, whether or not the brakes are applied. Existing systems in which control is cancelled only upon application of the vehicle brakes are defective in these latter respects.
A further disadvantage of many known systems of cruise control is that they are incompatible with and would disturb the operation of the governor systems applied to many vehicles, especially those with diesel engines.
The present invention is directed to providing a cruise control device of simple construction which may readily be fitted to most vehicles without any significant degree of modification of the latter, and without disturbing the operation of any existing governor device applied to the vehicle engine. Moreover the system can readily be arranged to disengage whenever the vehicle is sharply decelerated or travels down a steep hill.